Do Dogs Have Periods: Learning About the Estrus Cycle

If you have a female dog and haven’t spayed her, you may wonder why she is bleeding from time to time. You may have asked yourself, “Do dogs have periods?” Just like humans have regular cycles, so do female dogs. Once they are mature, at six months of age, they will menstruate. 

A dog’s period (or menstrual cycle) may be an alarming and slightly messy event, mainly because it corresponds with when the dog is in heat. But once you know what is happening, you’ll be able to help your dog, especially during the breeding season.

Do dogs have periods: The estrus cycle, and what it’s all about

Have you ever wondered if female dogs have periods? The answer is “Yes!”. The correct term for the menstrual cycle in dogs is the estrus cycle. Most commonly, when a dog is in heat, she is going through this cycle.

As your dog reaches puberty, it goes through this cycle. Smaller dog breeds tend to mature faster than larger dogs, and subsequently, a Chihuahua will be in heat sooner than, for example, a Labrador.

There are 4 distinct phases of the estrous cycle:

Phase 1 – Proestrus 

This is the first stage of the heat cycle when you may notice a blood-tinged discharge and some swelling. Your dog won’t allow mating during this cycle and may even come across as skittish.

How long are dogs in heat in the proestrus cycle? This phase lasts approximately 7-10 days but can last anywhere between a few days and up to 4 weeks. Symptoms of this phase include:

A personality change:

The cycle may affect a dog’s behavior, making them a bit angry or fearful. A menstruating dog can become more loving and needy with its owner, or she could become aggressive.

To help her, you can bathe her to clean the discharge up, give her extra love and affection, and keep the male dogs away from her.

Appetite changes:

It’s pretty common for a female dog to be uninterested in food during the first week of the dog heat cycle. However, some dogs may behave the opposite and desire more food.

Whatever the change happens to be, pay attention, as this may indicate that the first part of the heat cycle has started.

Swelling of the vulva:

Some dogs will swell slightly, and others more so. The bleeding amount also varies between dogs and breeds.

Tail tucking:

Tail tucking occurs when the female dog tucks the tail to protect the vulva. It is indicated by tucking the tail between the leg or even by the dog sitting down if another dog (especially a male) approaches.

Frequent urination:

During her cycle, your dog will urinate more. Some female dogs may even mark their environment with strongly scented urine to attract a mate to show that they are in heat and need a mate.

Phase 2 – Estrus 

This is the middle part of the stage, commonly known as “the heat.” During this stage, the female dog will begin to allow mating to happen. This phase may last from 3 days to 3 weeks, with an average length of 9 days.

At this time, the female dog will release eggs for fertilization, and she may move her tail to one side. Since she is now ready for breeding, your dog may spend more time outside than usual. Symptoms during this time include:

Lightened discharge:

The discharge now moves from bright red color in the beginning to a lighter shade of pink. The swelling will begin to subside.


In the initial stage, she would tuck her tail as a way to ward off any male company, but at this stage, she begins to flirt to show she is ready for mating.

Phase 3 – Diestrus Stage 



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